Vapor phase method of making ammonium perchlorate

ABSTRACT

A method for making finely particulate ammonium perchlorate by vapor phase reaction between gaseous ammonia and anhydrous perchloric acid vapor. The gaseous ammonia and perchloric acid vapor are separately mixed with an inert carrier gas and the resulting mixtures reacted to form fine ammonium perchlorate particles. The ammonium perchlorate particles may be recovered by means of a dust bag filter.

United States Patent m1 Conrad VAPOR PHASE METHOD OF MAKING AMMONIUM PERCHLORATE [75] Inventor: Raymond Conrad, Russellville, Ala.

[73] Assignee: Thiokol Corporation, Bristol, Pa.

[22] Filed: Feb. 22, 1971 [21] Appl. No.: 117,513

[52] U.S. Cl. 423/476; 149/76 [51] Int. Cl C0lb 11/18 [58] Field of Search 23/85; 149/76; 423/476' [56] References Cited UNITED STATES PATENTS 3,728,169 4/1973 Diebold 423/476 X FOREIGN PATENTS OR APPLlCATlONS United Kingdom 23/85 Canada 23/85 [451 May 13, 1975 OTHER PUBLICATIONS Schumacher, Perch/crates Their Properties, Manufaclure, and Uses, Reinhold Pub. Corp. N.Y., 1960, p. 99.

Primary Examiner-Benjamin R. Padgett Assistant Examiner-E. A. Miller [57] ABSTRACT A method for making finely particulate ammonium perchlorate by vapor phase reaction between gaseous ammonia and anhydrous perchloric acid vapor. The gaseous ammonia and perchloric acid vapor are separately mixed with an inert carrier gas and the resulting mixtures reacted to form fine ammonium perchlorate particles. The ammonium perchlorate particles may be recovered by means of a dust bag filter.

6 Claims, 1 Drawing Figure VAPOR PHASE METHOD OF MAKING AMMONIUM PERCHLORATE This invention relates to the manufacture of ammonium perchlorate of a particle size adapted to be used in rocket propellants, and more particularly, to a novel method of making ammonium perchlorate in the form of ultra-fine particles.

Most solid rocket propellants are principally composed of a polymeric fuel-binder having a finely divided oxidizer, usually ammonium perchlorate, dispersed therein. The oxidizer, a curing agent for the polymeric binder, and certain special purpose ingredients known in the art are dispersed in the binder while the latter is in viscous fluid form, and the resulting mixture is cast in situ in a rocket motor casing at a temperature suffi:

cient to convert the binder to elastomeric form.

It is known that the efficiency and rate of combustion of a solid propellant can be maximized by increasing the area of contact between the oxidizer and other ingredients of the propellant composition and that this area of contact can be increased by reducing the particle size of the oxidizer. Consequently, rocket propellant oxidizers, prior to their incorporation in the fuelbinder, have customarily been subjected to one or more mechanical grinding operations. However, such grinding operations are subject to a number of disadvantages. Thus they involve a considerable explosion hazard and numerous precautions must be taken to minimize the risk of explosion. Moreover, the risk of explosion can never be completely eliminated. Also there is a tendency for the ammonium perchlorate to become contaminated by material removed from the grinder and grinding media. In addition, grinding is a relatively expensive and time-consuming procedure, and it has not been found possible to reduce the particle size of the oxidizer by grinding to the extent that it is desirable for highly efficient propellant combustion.

Because of the foregoing disadvantages various proposals have previously been made for producing finely particulate oxidizers other than by grinding. Thus U.S. Pat. No. 3,452,445 discloses a process for making fine particles of ammonium perchlorate by quick freezing of aqueous ammonium perchlorate. Freezing of the aqueous solution is effected by rapidly rotating a flask containing the solution in an acetone-dry ice bath. The ice thus formed is then sublimed under a reduced pressure to recover ammonium perchlorate particles having an average size of 1.7 to 2.l microns.

U.S. Pat. No. 3,222,231 discloses a process wherein a saturated aqueous solution of ammonium perchlorate at a temperature of 95C. is simultaneously agitated and subjected to ultrasonic vibrations over a period of several hours. As the solution cools, ammonium perchlorate crystals precipitate and are subsequently removed from the solution, washed with acetone and ether and dried. The product crystals had a particle size within the range 5 to 350 microns.

While such processes avoid the explosion hazards involved in mechanical grinding, the size of the ammonium perchlorate particles they produce is of the same order of magnitude as, or in some cases larger than, that produced by the grinding process. It is accordingly an object of the present invention to provide a process for preparing ammonium perchlorate having an average particle size less than that provided by prior processes. It is another object of the invention to provide a process for making ammonium perchlorate which eliminates the explosion hazard involved in the grinding operation referred to above. It is another object of the invention to provide a process for making ultra-fine ammonium perchlorate of high purity at a low unit cost. It is a still further object of the invention to provide a process wherein for any given production rate the quantity of material being processed is relatively small. Other objects of the invention will be in part obvious and in part pointed out hereafter.

The objects of the invention are achieved, in general, by a direct addition reaction of gaseous ammonia and substantially anhydrous perchloric acid vapor according to the following equation:

The gaseous ammonia and perchloric acid vapor are incorporated in an inert carrier gas and the two gas streams are mixed to cause the ammonia and perchloric acid to react to form a suspension of fine ammonium perchlorate particles in the carrier gas. The ammonium perchlorate particles can be recovered from the carrier gas in any suitable manner such as, for example, by a dust bag filter.

The anhydrous perchloric acid can be conveniently prepared by mixing an aqueous perchloric acid, containing say by weight of the acid, with fuming sulfuric acid as illustrated by the following equation:

HClOrZ H O 10 H SO 2 v 12 H 50 HClO,

When such a mixture is heated at a reduced pressure of say 1 mm. of Hg, and a temperature of say 25 to 80C., anhydrous perchloric acid is vaporized therefrom. The anhydrous perchloric acid vapor as thus prepared is then mixed with an inert carrier gas.

The diluent or carrier gas used in carrying out the process of the invention should be inert to the reactants and any of various gases may be used for this purpose. Suitable gases include nitrogen, helium, symmetrical difluorotetrachloroethane (Freon 113) and air. The concentrations of ammonia and perchloric acid vapor in the diluent gas streams are not critical and may vary from say 1 to 10% by volume. The ammonia and perchloric acid vapor are desirably used in approximately stoichiometrical proportions.

The reaction between the ammonia and perchloric acid to form a suspension of fine ammonium perchlorate in the carrier gas is exothermic and the suspension is desirably cooled before removal of the ammonium perchlorate particles therefrom. Cooling of the suspension can be effected by addition of atmospheric air thereto.

In order to point out more fully the nature of the present invention, reference will now be made to the accompanying drawing which shows diagrammatically an illustrative system for carrying out the process of the invention. Referring to the drawing, the numeral 10 generally designates a reaction chamber for carrying out the gas phase reaction between the ammonia and perchloric acid. A mixture of gaseous ammonia and inert carrier, e.g., nitrogen, containing say 5% by volume of ammonia is fed into reaction chamber 10 through a pipe 12 which is provided within chamber 10 with a discharge nozzle 14 arranged at an angle of about 45 to the longitudinal axis of the reaction chamber. In like manner a mixture of perchloric acid vapor and inert carrier gas containing say 5% by volume of perchloric acid vapor is fed to chamber through a pipe 16 having a discharge nozzle 18 arranged at an angle of about 45 to the longitudinal axis of chamber 10. The nozzles 14 and 18 are so arranged as to project the gas streams flowing therethrough toward one another to effect the desired mixing of the streams and reaction of the ammonia and perchloric acid therein. If desired. additional inert gas can be fed to chamber 10 through pipe 20.

The suspension of fine ammonium perchlorate particles in the inert carrier gas formed in chamber 10 leaves the chamber through the pipe 22. As pointed out above, the reaction of ammonia and perchloric acid is exothermic and the ammonium perchlorate suspension formed in chamber 10 is desirably cooled before being further processed. As shown in the drawing, chamber 10 is provided with air induction ports 24 and 26 through which atmospheric air can flow to effect this cooling. The fine ammonium perchlorate particles in the suspension leaving chamber 10 through pipe 22 are separated from the carrier gas in a dust bag filter. The ultra-fine particles thus obtained can be advantageously used in the formulation of propellant compositions.

It is, of course, to be understood that the foregoing description is illustrative only and that numerous changes can be made in the materials, proportions and conditions given above without departing from the scope of the invention as defined in the appended claims.

I claim:

1. The method of making fine ammonium perchlorate particles which comprises reacting gaseous ammonia with substantially anhydrous perchloric acid vapor to form finely particulate ammonium perchlorate and recovering the particulate ammonium perchlorate thus formed.

2. A method according to claim 1 wherein the gaseous ammonia and perchloric acid vapor are reacted in approximately stoichiometrical proportions.

3. The method of making fine ammonium perchlorate particles which comprises forming a mixture of gaseous ammonia and an inert gas, forming a mixture of inert gas and substantially anhydrous perchloric acid vapor, mixing the ammonia-containing gas and the perchloric acid containing gas to form a gaseous suspension of fine ammonium perchlorate particles, and recovering the ammonium perchlorate particles from said suspension.

4. A method according to claim 3 wherein the ammonium perchlorate particles are separated from said suspension in a dust bag filter.

5. The method of making fine ammonium perchlorate particles which comprises forming a mixture of about 1 to about 10% by volume of ammonia and an inert gas, forming a mixture of about 1 to about 10% by volume of substantially anhydrous perchloric acid vapor and an inert gas, mixing the ammonia containing gas and the perchloric acid containing gas to form a gaseous suspension of fine ammonium perchlorate particles and recovering the ammonium perchlorate particles from said suspension.

6. The method of making fine ammonium perchlorate particles which comprises forming a mixture of gaseous ammonia and an inert gas, forming a mixture of inert gas and substantially anhydrous perchloric acid vapor, mixing the ammonia-containing gas and the perchloric acid containing gas to form a gaseous suspension of fine ammonium perchlorate particles, adding air to said gaseous suspension to cool it and recovering the ammonium perchlorate particles from the cooled suspension. 

1. THE METHOD OF MAKING FINE AMMONIUM PERCHLORATE PARTICLES WHICH COMPRISES REACTING GASEOUS AMMONIUM PERCHLORATE PARTITIALLY ANHYDROUS PERCHLORIC ACID VAPOR TO FORM FINELY PARTICULATE AMMONIUM PERCHLORATE AND RECOVERING THE PARTICULATE AMMONIUM PERCHLORATE THUS FORMED.
 2. A method according to claim 1 wherein the gaseous ammonia and perchloric acid vapor are reacted in approximately stoichiometrical proportions.
 3. The method of making fine ammonium perchlorate particles which comprises forming a mixture of gaseous ammonia and an inert gas, forming a mixture of inert gas and substantially anhydrous perchloric acid vapor, mixing the ammonia-containing gas and the perchloric acid containing gas to form a gaseous suspension of fine ammonium perchlorate particles, and recovering the ammonium perchlorate particles from said suspension.
 4. A method according to claim 3 wherein the ammonium perchlorate particles are separated from said suspension in a dust bag filter.
 5. The method of making fine ammonium perchlorate particles which comprises forming a mixture of about 1 to about 10% by volume of ammonia and an inert gas, forming a mixture of about 1 to about 10% by volume of substantially anhydrous perchloric acid vapor and an inert gas, mixing the ammonia containing gas and the perchloric acid containing gas to form a gaseous suspension of fine ammonium perchlorate particles and recovering the ammonium perchlorate particles from said suspension.
 6. The method of making fine ammonium perchlorate particles which comprises forming a mixture of gaseous ammonia and an inert gas, forming a mixture of inert gas and substantially anhydrous perchloric acid vapor, mixing the ammonia-containing gas and the perchloric acid containing gas to form a gaseous suspension of fine ammonium perchlorate particles, adding air to said gaseous suspension to cool it and recovering the ammonium perchlorate particles from the cooled suspension. 